Character generator



, D. J. PUGH ETAL lCHARACTERCTEIQERATORA April 29, 1969 n Filed June 15,19.66

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.N...`||` .5o i .229m ,Ibiomo; m uw] r L\. /m l S /S S v 4 Y v\\ .5523 IQ 20:84h@ S United States Patent ce 3,441,768 Patented Apr. 29, 1969U.S. Cl. 313-68 8 Claims ABSTRACT F THE DISCLOSURE An electron dischargedevice for generating a signal representative of selective characters orsymbols wherein a charge pattern on a composite target is converted toan electrical signal representative of the characters or symbols, thecomposite target including a pin face plate and character matrix incontact therewith.

This invention relates in general to electron discharge devices, andmore particularly, to a means for generating video signals representingselective characters, including the letters of the alphabet, numerals,punctuation marks and other symbols and indicia which may be used fordisplay purposes or for other uses.

Direct viewing character tubes wherein an electron beam is caused tointercept a selective character shaped aperture in a matrix prior toimpingement on a phosphor screen for display of characters and otherindicia is well known; however, where an electrical signal representinga character or other symbol is required for remote display or operationof diverse equipment, difliculty is encountered in converting the visualdisplay into an electrical signal of satisfactory quality.

In addition, other special discharge devices which are known provide forcharacter generation having an output signal representing a selectedcharacter while also providing visual display; however, these devicesare constructed so that the character matrix plates cannot be readilychanged after the tube is evacuated and sealed, and have thereforeproved generally unsatisfactory for many applications.

It is therefore an object of the instant invention to provide a devicefor generating a signal representative of selective characters orsymbols, which device eliminates, or substantially overcomes, thedeciencies inherent in prior art devices of a similar nature.

It is another object of the instant invention to provide a device forgenerating a signal representative of selective characters or symbolswhich is highly sensitive and ecient in operation.

It is another object of the instant invention to provide a charactergenerator of the type described which is of simple construction,providing for economic manufacture thereof, and is reliable andtrouble-free in use.

These and other objects, features and advantages of the instantinvention will become more apparent from the following detaileddescription of the invention, when taken in conjunction with theaccompanying drawings, which illustrate one embodiment of the instantinvention, and wherein:

FIGURE 1 is a schematic diagram of an electron discharge device inaccordance with the instant invention;

FIGURE 2 is a plan view, partially in detail, of the pin face electrodeutilized in conjunction with the instant invention;

FIGURE 3 is a plan view of an aperture matrix utilized in conjunctionwith the instant invention; and

FIGURE 4 is a partial sectional view of the target assembly which formspart of the instant invention.

In brief, the invention provides an electron discharge device of thecathode ray type wherein an electron beam of low velocity is projectedtoward a target consisting of a pin face having a charge patterngenerated across the surface thereof in the form of the characters orsymbols to be generated by the device. The low velocity electron beam ismodulated by the charge pattern as it approaches the immediate vicinityof the pin face target in accordance with the character or symbol of thecharge pattern which is scanned, a deflection system being provided toselect under control of an exterior selection signal one or more of theavailable characters or symbols provided on the charge pattern. The lowvelocity beam is caused to reach substantially zero velocity in thevicinity of the target, where it is modulated by the charge patternthereon and is returned by the electrostatic eld in the deviceback inthe direction of the cathode to be collected on a collector electrode.The signal derived from the collector electrode is thus in the form ofvideo signal modulated in accordance with the symbol or character thatis scanned.

Referring now to the drawings, and particularly to FIG- URE l thereof,an electron discharge device in accordance with the instant invention isrepresented generally at 10, having a generally cylindrical glassenvelope 11 which is evacuated in the well-known manner. The particularshape of the envelope 11 is not a particular part of the instantinvention, and could be provided in any form which will accommodate theelectrodes required by the invention and facilitate the operation of thedevice.

The evacuated envelope 11 contains an electron beam generating device 12which preferably takes the form of a conventional electron gunconstruction, including a conventional cathode, control grids, andanodes necessary to generate and project an electron beam E along thetube envelope 11 toward a target 13 consisting of a pin face 14, amatrix 15 contacting the pin face plate 14 and an electricallyconductive plate electrode 16 in contact with the other face of thematrix 15 and connected to a suitable potential. As illustrated inFIGURE l, the target assembly 13 is positioned at the extreme end of theenvelope 11 opposite to the beam generating means 12, and is sealed tothe glass walls of the envelope 11 with suitable electrical connectionsto the plate electrodes 16 and the pin face 14 preferably extendingdirectly out of the side walls of the envelope 11. Of course, otherarrangements for supplying electrical potentials to these and the otherelectrodes of the device may be adopted without departing from thespirit and scope of the invention.

An electrically conducting coating 17 on the inside surface of theenvelope 11 serves as an accelerating anode for the electron beam E andis connected to the positive side of DC voltage source 19 to provide thenecessary relative potential with the beam generating means, which isconnected to ground potential, to accelerate the beam along the axis ofthe evacuated envelope in the direction of the target assembly 13.Although not specifically illustrated in the drawings, a magnetic iieldgenerating means may be provided along the exterior of the envelope inconcentric relationship to the accelerating anode 17 to provide an axialmagnetic field within the tube envelope to focus the electron beam Efrom the beam generating means 12 to a small spot on the target assembly13. However, as will be apparent from the following discussion, sinceextreme accuracy of alignment of the beam between the generating means12 and the target assembly 13 is unnecessary under most circumstances,the provision of such a magnetic field generating means in connectionwith the instant invention is optional.

The device of the instant invention provides for protection of theelectron beam E into the vicinity of the target assembly 13 such thatthrough application of the proper potentials to electrodes 17 and 18 thevelocity of the beam in the vicinity of the target assembly 13 willbecome substantially zero. At this point, a modulation of the Abeam iseffected and the beam is then returned along substantially the same pathas it traveled from the beam generating means 12 to a point where it isintercepted by a collector electrode 20. In order to reduce the velocityof the electron beam E in the vicinity of the target assembly 13, adecelerating ring in the form of a conductive coating 18 on the innersurface of the envelope 11 between the target assembly 13 and the anode17 is provided. The decelerating ring 18 is connected to a source ofpositive potential which is much lower than than the voltage to whichthe accelerating anode 17 iS connected so that a deceleration of thebeam as it passes from the area of the accelerating anode 17 to the areaof the decelerating ring 18 and target assembly 13 occurs.

The pin face 1'4 is provided with a conductive background Which ispreferably connected to ground potential along with the cathode in thebeam generating means 12 so that -in the absence of a charge pattern onthe pin face 1-4, the electron beam E will return along substantiallythe same path as taken from the beam generating means 12 due to thevoltage gradient produced between the pin face 14 and the deceleratingring 18 and anode 17 and will be intercepted by the collector electrode20. However, if a charge pattern Iis placed upon the surface of the pinface 14 facing the beam generating means 12 and the beam is scannedacross this charge pattern, in the areas of the pin face surface Wherethe pins are charged to a positive potential, electrons from the beam Ewill be drawn to the pin face and therefore will be removed from thebeam so that an appreciably smaller number of electrons will return tothe collector electrode 20. As the beam passes over areas of the pinface 14 containing pins which are not externally charged, substantiallyall of the electrons from the beam will return to the collectorelectrode 20 so that as the beam is swept over the charge pattern amodulated signal is collected by the collector electrode 20, whichsignal represents the pattern over which the beam has passed.

As seen in FIGURE 2, the pin face 14 preferably consists of a pluralityof closely spaced minute conductive pins which are electricallyinsulated from one another so that each pin may carry its own selectivecharge potential. A charge pattern is created on the surface of the pinface 14 by providing a matrix 15 containing apertures thereinrepresenting various characters and symbols, such as the letters of thealphabet, numerals, punctuation marks, etc., in contact with the surfaceof the pin face 14 so that a potential applied to the matrix 15 byconductive plate 16 is transferred to all of the pins in the pin face 14which contact the matrix 15.

As is apparent, those pins which intercept the spaces in the matrix 15representing the various characters or symbols will receive a negativepotential from `the beam, while pins contacting the matrix plate areheld at a positive potential. The result is the creation of a chargepattern across the surface of the pin face 14 facing the beam generatingmeans 12 with the various characters and symbols provided thereinappearing as negatively charged areas.

As the beam generated and projected by the beam generating means 12reaches the vicinity of the pin face 14 at zero velocity, it ismodulated by the charge pattern on the pin face so that the returningbeam intercepted by the collector electrode 20 represents the characteror characters over which -the beam has been directed. In order toprovide selection of one or more of the characters or symbols in thecharge pattern provided on the surface of the pin face 14, a magneticdeflection system 21 including a deflection control circuit 22 isprovided on the exterior of the cathode ray device so that the beam maybe horizontally and vertically deflected to cover any one or any groupor symbols in the charge pattern. While a magnetic deflection system isprovided in the illustrated embodiment, it is apparent that thedeflection of the beam to scan one or more characters in the chargepattern can also be effected with equal facility and response by anelectrostatic deflection system of known construction providing`orthogonally disposed electrostatic deflection plates.

While any known pin face construction having a plurality of closelyspaced minute conducting pins disposed in insulated relationship to oneanother may be effectively utilized with the instant invention, aparticular pin face construction has been used with particularlyadvantageous results with the instant invention. Looking to the partialsectional view of the target assembly 13 illustrated in FIGURE 4, theplate electrode 16 is seen -to be in electrical contact with the matrix15 having apertures 15a therein forming the various characters andsymbols to be generated by the device in accordance with the invent-ion.In contact with the face of the matrix 15 opposite to that of the plateelectrode 16, is the pin face 14 which consists of a Aplurality ofminute conducting pins 25 surrounded by a jacket 26 of electricallyinsulating material, such as glass, which jacket 26 is in turnsurrounded by a sleeve 27 of conductive material, such as copper,stainless steel, or other suitable conductive metal. The conductivesleeves 27 in the pin face 14 are in electrical contact with adjacentconductive sleeves 27 of other pin assemblies in the pin face, so thatthe pin face 14 effectively consists of a metallic conductive discformed by the interconnected electrically conductive sleeves 27 having aplurality of apertures therein into which the insulating glass jackets26 containing the pins 25 are inserted.

With this construction, the pins 25 are accurately positioned and evenlyspaced over the surface of the pin face 14 and are electricallyinsulated from the conductive portion of the disc which may be connectedto ground potential along with the cathode of the beam generating means12 thereby providing the reference potential for the positive chargesapplied to selective pins by way of the plate electrode 16 and matrix15. Thus, in the absence of a charge pattern applied to the pin face 14by the plate electrode 1'6 and matrix 15, a substantial portion of thesurface `of the pin face 14 will be at ground potential providing thenecessary eld gradient in combination with the decelerating ring 18 forreturn of the electron beam in its entirety to the collector electrode20.

Since the charge pattern which is generated across the surface of thepin face 14 is derived from direct contact by the individual pins 25with a positive voltage source by way of plate electrodes 16 and matrix15, a high accuracy of representation of the characters to be generatedby the device in accordance with the invention is provided for purposesof modulating the electron beam thereby providing a continuousdependable response with high resolution and accuracy not heretoforeattainable in character generating devices of much less simplicity. Inaddition, by providing proper spacing of the characters on the matrix15, extreme accuracy in the deflection system 21 and deflection control22 is not necessary, thereby eliminating a need for special means forcontrolling the linearity of the path of the electron beam generatingmeans 12 to the target assembly 13. However, as indicated above, if alarge number of characters or symbols are provided on the matrix 15requiring accurate control of the path of the electron beam due to theclose spacing of these symbols, a magnetic field generating means (notshown) may be disposed about tbe envelope 11 of the discharge device tocreate an axial magnetic field guiding the electron beam along a linearpath as determined by the deflection means 21.

It is also within the contemplation of the invention to provide a matrix15 made of electrically insulating material and having the aperturesthereof in the form of characters or symbols llled with a metal of goodelectrical conductivity. In this case, the positive potential from plateelectrode 16 will be transferred only to pins 25 in contact with theconductive fillings. The charge pattern produced on the surface of thepin face plate 14 will then appear as positive characters on anuncharged background. The disadvantage with this arrangement is that anegative signal is generated at collector electrode 20.

Although only one embodiment of the invention has been disclosed anddescribed herein, it is to be expressly understood that various changesand substitutions may Ibe made therein without departing from the spiritof the invention as well understood by those skilled in the art. Forexample, other pin face constructions than the one specificallydisclosed and illustrated herein may be utilized in accordance with theinvention, as well as other types of collector electrodes for thereturning electron beam, for example, an electron multiplier collectorelectrode arrangement of the type well known in the art. Reference,therefore, will be had to the appended claims for a definition of thelimits of the instant invention.

We claim:

1. A character generator in the form of an electron discharge devicecapable of generating a video signal representing a selective characteror symbol, comprising:

an evacuated envelope,

target means positioned at one end of said envelope providing a chargepattern including a plurality of characters or symbols on one facethereof,

beam generating and projecting means within said envelope for projectingan electron beam along the axis thereof toward said one face of saidtarget means, and

output means operatively associated with said target means for providinga signal representative of said charge pattern,

said target means including aperture matrix means for creating saidcharge pattern, a pin face plate in contact with said aperture matrixmeans, and means for applying a predetermined potential to said aperturematrix means.

2. A character generator in the form of an electron discharge devicecapable of generating a Video signal representing a selective characteror symbol, comprising:

an evacuated envelope,

target means positioned at one end of said envelope providing a chargepattern including a plurality of characters or symbols on one facethereof,

beam generating and projecting means Within said envelope for projectingan electron beam along the axis thereof toward said one face of saidtarget means, and

output means operatively associated with said target means for providinga signal representative of said charge pattern,

said target means being provided as a composite element includingaperture matrix means for creating said charge pattern, a pin face platehaving a plurality of conductive pins insulatingly supported so as to beevenly spaced across the surface thereof, said aperture matrix meansbeing in contact with the side of said pin face plate opposite said beamgenerating and projecting means, and means for applying a predeterminedpotential to said aperture matrix means such that said predeterminedpotential is applied to all pins contacting said aperture matrix means.

3. A character generator as defined in claim I2 wherein said aperturematrix means is in the form of a conductive electrode having a pluralityof apertures therein in the shape of selected characters or symbols.

4. A character generator as defined in claim 3 wherein the apertures insaid aperture matrix means are of suficient size to each intercept aplurality of conductive pins in said pin face plate.

5. A character generator as defined in claim 2 wherein said aperturematrix means is in the form of an electrode of insulating materialhaving a plurality of apertures therein in the shape of selectedcharacters or symbols, said apertures being filled with an electricallyconductive material.

6. A character generator as defined in claim 2 further includingelectron beam deflection means for scanning said electron beam over aselected one of the character charge images on said target means.

7. A character generator in the form of an electron discharge devicecapable of generating a video signal representing a selective characteror symbol comprising:

an evacuated envelope;

target means positioned at one end of said envelope providing a chargepattern including a plurality of characters or symbols on one facethereof,

beam generating and projecting means within said envelope for projectingan electron beam along the axis thereof toward said one face of saidtarget means,

electrode means positioned between said beam generating and projectingmeans and said target means for decelerating said electron beam to zerovelocity at a point in proximity to said target means and for returningsaid electron beam in the direction of said beam generating andprojecting means, and

collector means in the vicity of said beam generating and projectingmeans for collecting the returning electron beam,

said target means including aperture matrix means for creating saidcharge pattern so as to effect modulation of said electron beam as itcomes into proximity with said target means,

said target means being in the form of a composite constructionincluding a pin face plate having a plurality of conductive pinsinsulatingly supported Within a conductive ground plane so as to beevenly spaced across the surface thereof, said aperture matrix meansbeing in contact with the side of said pin face plate opposite said beamgenerating and projecting means, and means for applying a positivepotential to said aperture matrix means such that said positivepotential is applied to all pins contacting said aperture matrix means.

8. A character generator as defined in claim 7 wherein said means forapplying a positive potential to said aperture matrix means includes apositive voltage source, said ground plane of said pin face plate andsaid beam generating means being connected to ground potential.

References Cited UNITED STATES PATENTS 2,015,570 9/1935 Sabbah et al.313-83 XR 2,925,507 2/1960 Keeran 315-21 XR 2,964,672 12/1960 Nixon315-21 2,976,447 3/ 1961 McNaney.

3,284,658 ll/ 1966 Winfield.

RODNEY D. BENNETT, JR., Primary Examiner.

MALCOLM F. HUBLER, Assistant Examiner.

U.S. Cl. X.R.

